From: Christoph Hellwig <hch@lst.de>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
Li Feng <fengli@smartx.com>, Jens Axboe <axboe@kernel.dk>,
"Michael S. Tsirkin" <mst@redhat.com>,
Jason Wang <jasowang@redhat.com>,
Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
"open list:BLOCK LAYER" <linux-block@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>,
"open list:VIRTIO BLOCK AND SCSI DRIVERS"
<virtualization@lists.linux.dev>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] virtio_blk: set the default scheduler to none
Date: Thu, 7 Dec 2023 16:19:17 +0100 [thread overview]
Message-ID: <20231207151917.GA20401@lst.de> (raw)
In-Reply-To: <CABgObfYJUH0hF8QfNUAZS9ztR7LqeHGOXeTa0JO904svJw23_g@mail.gmail.com>
On Thu, Dec 07, 2023 at 03:55:17PM +0100, Paolo Bonzini wrote:
> > This seems similar to commit f8b12e513b95 ("virtio_blk: revert
> > QUEUE_FLAG_VIRT addition") where changing the default sounded good in
> > theory but exposed existing users to performance regressions. [...]
> > I don't want to be overly conservative. The virtio_blk driver has
> > undergone changes in this regard from the legacy block layer to blk-mq
> > (without an I/O scheduler) to blk-mq (mq-deadline).
>
> IIRC there were also regressions in both virtio-blk and virtio-scsi
> when switching from the legacy block layer to blk-mq. So perhaps I
> *am* a bit more conservative, but based on past experience, this patch
> seems not to be a great idea for practical use cases.
Agreed. I'm in fact not exactly happy about the rather odd
BLK_MQ_F_NO_SCHED_BY_DEFAULT flag to start with.
next prev parent reply other threads:[~2023-12-07 15:19 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-07 4:31 [PATCH] virtio_blk: set the default scheduler to none Li Feng
2023-12-07 6:02 ` Jason Wang
2023-12-07 6:32 ` Li Feng
2023-12-07 6:38 ` Michael S. Tsirkin
2023-12-07 6:53 ` Chaitanya Kulkarni
2023-12-07 7:21 ` Li Feng
2023-12-07 9:48 ` Chaitanya Kulkarni
2023-12-07 14:51 ` Stefan Hajnoczi
2023-12-07 14:55 ` Paolo Bonzini
2023-12-07 15:19 ` Christoph Hellwig [this message]
2023-12-08 2:00 ` Ming Lei
2023-12-08 2:44 ` Keith Busch
2023-12-08 3:15 ` Jens Axboe
2023-12-08 3:54 ` Ming Lei
2023-12-08 5:55 ` Li Feng
2023-12-08 11:07 ` Paolo Bonzini
2023-12-25 14:20 ` Michael S. Tsirkin
2023-12-26 9:01 ` Li Feng
2023-12-26 9:05 ` Michael S. Tsirkin
2023-12-26 12:14 ` Li Feng
2023-12-26 15:38 ` Michael S. Tsirkin
2023-12-27 7:26 ` Li Feng
2023-12-27 10:06 ` Michael S. Tsirkin
2023-12-28 7:25 ` Li Feng
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